Braking pressure regulating device

ABSTRACT

A braking pressure regulating device, in particular an anti-lock control device for hydraulic brake systems of automotive vehicles, comprising a master cylinder and a pressure modulator for the variation of the hydraulic pressure in the wheel cylinders during the braking pressure control mode. The device is equipped with a motor-driven pump (8) for generating a hydraulic pressure and with an electronic control unit (5) for controlling the valves of the pressure modulator (2). During the braking pressure control mode, the working chambers (10, 15) of the master cylinder (16) are exposed to pump pressure. Caused by the pump pressure in the working chamber (10), the push rod piston (11) and thus the brake pedal (1) disadvantageously are returned into their basic position in prior-art devices. The present arrangement provides that the switching positions of the regulating valve incorporated in the push rod piston are shifted into the cylinder during the braking pressure control mode. Therefore the brake pedal is not fully reset during the control mode. The operating comfort of the brake pedal is thereby augmented.

BACKGROUND OF THE INVENTION

The present invention relates to a braking pressure regulating device,in particular an anti-lock control device, traction slip control devicefor hydraulic brake systems of automotive vehicles, comprising a mastercylinder with at least one working piston, (push rod piston and/orfloating piston) and at least one working chamber, a supply reservoirfor pressure fluid, a pressure modulator for the variation of thehydraulic pressure in the wheel cylinders of the wheel brakes during thebraking pressure control mode, the said pressure modulator includinginlet and outlet valves for the wheel cylinders, an electronic controlunit for the control of the valves of the modulator, at least onemotor-driven pump for generating a hydraulic pressure, the workingchamber of the master cylinder being applied by pump pressure in thebraking pressure control mode and the working piston of the mastercylinder being movable in the direction of its initial position causedby the pump pressure, a regulating valve being provided in at least oneworking piston which, in the braking pressure control mode, regulatesthe pressure fluid flow in the hydraulic fluid cycle that is composed ofpump, working chamber of the master cylinder, supply reservoir (pressurefluid flow regulation).

Braking pressure regulating devices, in particular in the form ofanti-lock systems, are used in the motor vehicle industry inincreasingly large numbers. In specific categories of these anti-locksystems, hydraulic pumps are used for generating an auxiliary pressureduring the control mode.

A like anti-lock device has become known from e.g. German publishedpatent application DE-OS 36 41 712.2.

This application describes a valve for a brake system with slip control,with a pedal-operated, preferably auxiliary-force assisted brakingpressure generator, with a master cylinder to which the wheel brakes areconnected via main brake lines, with hydraulic auxiliary-pressure pumpsas well as with wheel sensors and electronic circuits for determiningthe wheel rotational behaviour and for generating electric brakingpressure control signals permitting to control electromagneticallyactuatable pressure-fluid inlet valves and outlet valves inserted forslip control into the pressure fluid lines, with the pistons of themaster cylinder comprising valves which, in the brake's releaseposition, open pressure-fluid connections between the pressure fluidsupply reservoir and the pressure chambers and which close thesepressure-fluid connections in the braking position.

The special characteristics of this device reside in that valvesarranged in the pistons of the master cylinder comprise in each case avalve member longitudinally slidable in a recess and cooperating in eachcase with an opening member, e.g. a tappet, in such a fashion that thetappet moves the valve member into its opened position when therespective piston is in its release position, with the tappet takingsupport on a stationary pivot, cross member or bolt, and with eachrecess being closed on the side facing the pressure chamber by means ofa bowl portion which serves as a support of the respective valve-closurespring.

In braking pressure regulating devices of the described known type, thepump pressure causes the brake pedal to return to its initial positionduring the control mode. This is not desirable in many events. Due tothis shift-back, the operating comfort for the driver is impaired.

It is an object of the present invention to devise a braking pressureregulating device wherein the brake pedal is not slid back into itsinitial position during the control mode.

Further, it should also be possible to achieve several positions of thebrake pedal in front of its initial position. Besides, it is principallydesired to improve the pedal feeling during the control mode.

These improvements are to be accomplished by means as simple aspossible, and the solution of the object is to be cost-efficient.

There should be need for only few and fail-safe component parts.

The need for additional sensors should be obviated. It should not benecessary to alter the brake power booster.

SUMMARY OF THE INVENTION

This object is achieved according to the instant invention in that meansare provided which, in the braking pressure control mode, displace theswitching positions of the regulating valve incorporated in the workingpiston (push rod piston and/or floating piston) into the mastercylinder.

Regulating valves are known which are incorporated as a centralregulating valve in the working piston and which are composed of a valveseat, a valve closure member, a tappet acting upon the valve closuremember and opening the regulating valve as well as a stop for thetappet.

In braking pressure regulating devices of the type initially referred towhich are equipped with the regulating valve described hereinabove, itis suggested to solve the objects at issue in that, in the brakingpressure control mode, the stop for the tappet is arranged to move bypredefined distances away from its initial position into the mastercylinder so that in the braking pressure control mode the pressure fluidflow control in the hydraulic fluid cycle takes place at positions ofthe working piston which are displaced into the master cylinder.

In another embodiment of this invention, there is provision ofhydraulic, electromagnetic, pneumatic or mechanic actuating means whichposition the stop for the tappet in the direction into the mastercylinder at a distance in front of its initial position.

When employing a hydraulic actuating means, in particular a hydraulicpiston-cylinder assembly, the pump pressure can be made use of forpressurization.

It is proposed in a preferred embodiment that the stop for the tappetconsists of a stop device which comprises a movable direct stop memberand a movable indirect stop member.

The movable indirect stop member can be arranged in a manner able to bepositioned by the pump pressure, on the one hand, and by the force of aspring element, on the other hand.

In further realising this idea, a separate pressure chamber can beprovided in the master cylinder which is confined by the movableindirect stop member and is variable in its volume. This movableindirect stop member can be designed as a piston which is displaceableby the pump pressure in opposition to the force of a spring.

In braking pressure regulating devices which, as an integral componentpart, comprise a brake power booster, in particular a so-called `vacuumbrake power booster`, it can be provided in an embodiment that thementioned separate pressure chamber in the master cylinder is formed ofthe master cylinder housing, the described displaceable piston and theforce-transmitting element of the brake power booster.

In a group of further embodiments of this invention, a mechanicalblocking unit is provided which, in the braking pressure control mode,positions the stop for the tappet in specific positions in front of theinitial position.

This blocking unit is maintained stationary by a fixing mechanism in oneor more positions in front of the initial position and is composed of asleeve accommodated in the master cylinder and having a stop element forthe tappet of the regulating valve, the said stop element beingpreferably composed of a component part (cross member) which is placedcrossly to the axis of the master cylinder and is designed in particularlike a pin, and which is located within the sleeve.

The fixing mechanism can be arranged in the master cylinder housing, inparticular in a way displaceable radially in opposition to the sleeve,and can fix said sleeve in one or more positions either by operativeengagement, e.g. by jamming, or by positive engagement, e.g. by means ofa profile.

For fixing by way of positive engagement, the sleeve can be furnishedwith a saw-tooth-shaped external profile.

In a special embodiment, the fixing mechanism is composed of a pistonwhich is guided in the master cylinder wall and is slidable by ahydraulic piston-cylinder assembly. This piston-cylinder assembly can beacted upon by the pressure fluid of the pump in the braking pressurecontrol mode.

In another embodiment, the fixing mechanism designed as a piston isdisplaced by an electromagnetic lifting mechanism, in particular by amagnet. This lifting mechanism can be controlled by the electroniccontrol unit of the braking pressure regulating device.

The fixing mechanism designed as a piston can be shifted by a pneumaticconverter against the sleeve in another embodiment. This pneumaticconverter uses the difference between the atmospheric pressure, on theone hand, and the pressure below atmospheric pressure in the suctionpipe of the internal combustion engine of the automotive vehicle or avacuum pump, on the other hand, and that is to say, for generating atranslatory force which acts upon the piston. The pneumatic convertercan be controlled by the electronic control unit of the braking pressureregulating device.

The above-described arrangement of blocking unit and fixing mechanism,more particularly according to the embodiments of FIGS. 3, 4, 5 can bearranged for the push rod piston or for the floating piston of a tandemmaster cylinder or for both pistons.

The instant invention affords the following advantages:

The mentioned shortcomings of the state of the art are eliminated andthe manifold requirements of the inventive objects are achieved. It isaccomplished by very simple means and at low costs that one or moreswitching positions of the regulating valve are reached which are placedin a manner shifted into the master cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention can be gathered from the followingdescription of several embodiments of this invention. These embodimentsare explained by way of five Figures.

FIG. 1 shows an anti-lock control device with a vacuum brake powerbooster.

FIG. 2 shows an embodiment of this invention.

FIG. 3 displays a cross-sectional view of a second embodiment.

FIGS. 4 and 5 show further embodiments.

DETAILED DESCRIPTION

The device according to FIG. 1 is to be considered as state of the art,it comprises the following aggregates: a vacuum brake power booster 9operated by the brake pedal 1, a tandem master cylinder 16, a modulator2 for the pressure control in the anti-lock mode, an electronic controlunit 5 for processing sensor signals and a hydraulic pressure pump 8which is driven by an electric motor 7.

FIG. 1 displays the apparatus in the release position. The pressurechambers 10, 15 of the master cylinder communicate in a known fashionwith the pressure-fluid supply reservoir 3 via open central regulatingvalves, via connecting channels in the interior of the pistons as wellas via an annular chamber in the intermediate piston, via bores and viahydraulic lines 19, 20.

The two pressure circuits 21, 22 of the master cylinder communicate withthe wheel brakes 27, 28, 29, 30 via electromagnetically actuatablevalves which are open in their initial position, that is to sayso-termed SO-valves (SO=opened in their de-energized state) or inletvalves 23, 24, 25, 26.

The parallel connected wheel brakes 27, 28 and 29, 30, respectively, areallocated to the diagonally arranged pressure circuits (brake circuits)21, 22. For the arrangement of the vehicle wheels corresponding to thementioned brakes, the following short terms have been used: VL for frontleft, HR for rear right, VR for front right, HL for rear left wheel. Thewheel brakes 27, 28, 29, 30 are connectible further viaelectromagnetically actuatable outlet valves 31, 32, 33, 34, so-termedSG-valves (SG =closed in their de-energized state) which shut off intheir inactive position, via a hydraulic return line 35 and via the line4 with the supply reservoir or pressure-compensating reservoir 3. Thevehicle wheels are equipped with electrical sensors 36, 37, 38, 39 whichcooperate with toothed discs co-rotating synchronously to the wheelrotation and which generate electric signals indicative of the wheelrotational behaviour, that means the wheel speed and variations of thisspeed. These signals are fed via the inputs 40, 41, 42, 43 to theelectronic control unit 5. This electronic control unit processes thesensor signals on the basis of a control algorithm memorized in it toform output signals (braking pressure control signals) which, in thebraking pressure control mode, serve to operate the SO-valves andSG-valves, in consequence whereof the braking pressures are decreased,are kept constant or re-increased in the individual wheel cylinders ofthe disc brakes corresponding to the control algorithm. To this end, theactuating magnets of the SO-valves and SG-valves are driven via theoutputs 44, 45, 46, 47 of the electronic control unit. The electricalconnecting lines between the ports 44, 45, 46, 47 and the coils of theSo-valves and SG-valves are not illustrated in the Figures. In thebraking pressure control mode, the electric motor 7 of the pump 8 is putinto operation. The switch-on signal is applied on the motor by theoutput 48 of the electronic control unit 5. In the control mode, thepump develops pressure in the pressure lines 49, 50, 51. These linesrepresent a pressure fluid conduit which is connected with the pressurefluid conduit of the tandem master cylinder, i.e. the pressure lines 21,22. That is to say, in the control mode, the pressure chambers 10, 15 ofthe tandem master cylinder are pressurized by the pump.

Upon brake application in the normal braking mode, the pedal force F istransmitted onto the master cylinder pistons boosted by the vacuum inthe booster 9. The central regulating valves in these pistons willclose, thus allowing braking pressure to develop now in the pressurechambers 10, 15 and hence in the brake circuits 21, 22 which propagatesvia the SO-valves 23, 24, 25, 26 to the wheel brake cylinders. Ondetection of an imminent locked condition at one or more of the wheelsby means of the sensors 36, 37, 38, 39 and the electronic control unit5, the anti-lock control mode will commence. The drive motor 7 of thepump 8 will be switched on, whereby pressure develops in the pressurelines 49, 50, 51 which, on the one hand, is applied on the wheelcylinders of the wheel brakes via the SO-valves and, on the other hand,pressurizes the pressure chambers of the master cylinder, as isillustrated. In consideration of the control algorithm, further signalsof the electronic control unit will cause change-over of theelectromagnetically actuatable SO-valves and SG-valves.

The pump pressure in the working chambers 10 and 15 cause the workingpistons 11 and 12 in FIG. 1 to displace to the right. The push rodpiston 11 moves until its right-hand stop 6 (FIG. 1) in the prior-artbrake power boosters. As a result, the brake pedal 1 is reset, itassumes its initial position. That is to say, the driver's foot pushesagainst a reset pedal.

In this position, the central valves of the push rod piston 11 and ofthe intermediate piston 12 will open. Pressure fluid can flow back viathese central valves into the supply reservoir 3 in a manner known perse via the return lines 19 and 20.

As regards the intermediate piston, this is effected via theunpressurized annular chamber of the intermediate piston. As regards thepush rod piston, this is effected via the unpressurized supply chamber13, the supply bore 14 into the return line 20. During the entirecontrol mode, the working pistons are retained in their initialposition. Likewise the brake pedal is retained in its initial positionduring the entire control mode.

FIG. 2 illustrates the master cylinder in the area of the push rodpiston in more detail.

As a whole, the push rod piston is referred to by 11. Reference numeral10 designates the working chamber which is pressurized by the push rodpiston. 13 designates the unpressurized supply chamber which is incommunication with the supply reservoir via the lines 14 and 20.

The push rod piston 11 comprises an inside bore 52. Accommodated in thisbore is the central valve composed of spherical closure member 53 andvalve seat 54.

When, due to the pump pressure in the working chamber 10, the push rodpiston in FIG. 2 is displaced to the right, the tappet 55 will move intoabutment on the cross pin 56.

The tappet lifts the spherical closure member 53 from the valve seat 54so that pressure fluid can propagate out of the pressure chamber 10through the central valve and the radial bores 57 into the chamber 13and from there via the lines 14 and 20 into the supply reservoir.

In the prior art, this took place in the right-hand end position of thepush rod piston. Hence, the brake pedal was returned completely to itsinitial position in the prior art. In the embodiment of this inventionaccording to FIG. 2, it is arranged for that pump pressure is introducedinto the pressure chamber 59 via a pressure line 58.

This line 58 can be an external line or a line which is composed ofbores n the master cylinder housing.

The pressure chamber is formed of the master cylinder bottom 60, themaster cylinder housing 16, the piston 61 and the push rod 62 of thevacuum brake power booster 9. The seal 63 is provided for sealing thepressure chamber.

In the normal braking mode, the push rod piston 11 is displaced to theleft into the master cylinder.

Upon commencement of the braking pressure control mode, chamber 59 willbe exposed to pump pressure. This pump pressure causes the piston 61 todisplace to the left in FIG. 2.

Spring 64 is compressed as a result. Via the sleeve-shaped spacer 65,the stop pin for the tappet 55, or cross pin 56, is moved to the leftduring the control mode.

As can be gathered from FIG. 2, the cross pin or stop pin 56 is arrangedcrossly in a recess 66 in the push rod piston.

In the braking pressure control mode, i.e. upon pressurization ofchamber 59, the cross pin 56 will move away from the rear wall 67 of therecess 66 in the push rod piston in the direction of the right-hand endof the tappet 55.

Finally, the cross pin 56 abuts as a stop on the tappet 55.

That is to say, in the control mod, opening of the central valve isachieved by the tappet 55 in front of the right-hand initial position ofthe working piston.

Compared to its initial position, the position of the push rod piston inthe master cylinder is shifted into the master cylinder.

Now the control function known per se of valve 53, 54 will commence, andnamely in the braking pressure control mode, e.g. in the anti-lockcontrol mode, in a position of the push rod piston which is shifted intothe master cylinder when compared to the initial position of the pushrod piston.

Consequently, the brake pedal which is coupled with the push rod pistonin terms of effect by way of the vacuum brake power booster and thepedal assembly, will not be moved back into its extreme initial positionin the control mode. Upon actuation, the brake pedal will remain inpositions placed before the initial position.

Owing to these shifted positions, the driver's brake pedal feeling willbe remarkably improved in the control mode.

Spring 64 is a spring of lesser total height. For instance, a Bellevillespring with a corresponding characteristic curve can be used. Themovement of the piston 61 to the left is possible because pump pressureis prevailing on its right-hand side, whilst solely the force of thespring 64 that is to be dimensioned correspondingly is acting from theleft. Besides, no hydraulic pressure is prevailing on the left side ofpiston 61, since the supply chamber 13 is unpressurized, as is shown.

In FIG. 3, reference numeral 68 shows that part of a master cylinderhousing which houses a mechanical blocking unit for the tappet 72 of thecentral regulating valve and a fixing mechanism for positioning thisblocking unit.

Housed inside the master cylinder which, as a whole, is referred to by69 is a sleeve 70. This sleeve has a cross pin 71. Said cross pin servesas a stop for the tappet 72 of the regulating valve. Thus, sleeve withcross pin block the tappet when it tends to move also to the right inconsequence of a movement of the working piston to the right. Thearrangement of sleeve 70 and cross pin 71 designed as blocking unit canbe fixed in several positions left of its initial position by way of thepiston 86 serving as fixing mechanism.

The regulating valve itself is composed of a ball 73 and a valve seat74. This ball is applied by the pressure of spring 75. As can be takenfrom FIG. 3, the ball can be lifted by the tappet from the valve seat.

FIG. 3 illustrates a piston shaft 76 and a piston end. This piston end77 comprises a seal 78 sealing the working chamber 79 of the mastercylinder. A recess 80 is provided in the piston shaft 76. Cross pin 71is located inside this recess. Piston end 77 serves as a stop for sleeve70. When the brake is released, that means when the piston end returnsinto its right-hand initial position, the piston end will entrain sleeve70 in the direction to the right.

The master cylinder has a housing attachment 81 that is ofcylinder-shaped design as well as a closure member 83 furnished with aseal 82.

A hydraulic piston-cylinder assembly is accommodated in thecylindrically designed attachment 81. The cylinder is formed by thepressure chamber 84. The piston is designed as a converter piston 85. Itconverts the pump pressure prevailing in the chamber 84 during thecontrol mode into a force which acts upon the end of the piston rod ofthe converter piston, the said end being designed as piston 86. 87 is aclosure member for sealing the chamber 84. Piston 86 is furnished withthe seal 113.

The mode of operation of the embodiment according to FIG. 3 will bedescribed hereinbelow.

The pedal force boosted by the brake power booster acts upon the pushrod 88 in the direction to the left. The push rod displaces the pistonconsisting of piston shaft and piston end to the left.

The position of the piston shaft and/or piston end is of decisiveimportance for the pedal's position.

In the normal braking mode, pressure develops in the working chamberwhen the piston end is displaced to the left. This pressure is alsoprevailing in the chamber 89 which is hydraulically connected with theworking chamber through the opening 111. Caused by the rising pressurein chamber 79, the ball 73 is pressed onto the valve seat.

In another movement of the piston shaft to the left, the rear wall 90 ofthe recess 80 of the piston shaft comes into abutment on the cross pin.Caused thereby, cross pin and sleeve 70 are moved to the left into themaster cylinder.

There is sufficient distance between cross pin 71 and tappet 72 of thecentral valve in the normal braking mode. Hence follows that thepressure development in the master cylinder can be performedcorresponding to the pedal force.

After sleeve 70 has been moved a specific distance into the mastercylinder caused by the rear wall 90 abutting on the cross pin 71 andthus by virtue of the piston shaft 76, it is now to be assumed forfurther description of the mode of function that an anti-lock controlmode sets in.

The working chamber 79 is applied by pump pressure in the control mode.As a result, the working piston composed of piston end and piston shaftis moved to the right.

At the same time, sleeve 70 is blocked by piston 86, i.e. the sleeve isfixed in its instantaneous position slid into the cylinder.

Fixing of the sleeve in its inshifted position takes place as follows:

Under the effect of the hydraulic pressure in chamber 84, piston 86 ispressed radially against the sleeve and jams it in the master cylinderhousing. Thus, the cross pin 71 assumes a predefined position which isin front of the initial position. That means the cross pin as stop forthe tappet 72 is moved into the cylinder and is positioned there in thecontrol mode.

As is illustrated, the working piston consisting of piston end andpiston shaft moves to the right in the control mode. Tappet 72 movesagainst the cross pin 71 serving as stop. Tappet 72 disposed on the stoplifts the ball 73 from the valve seat 74. Pressure fluid can thus flowout of the working chamber 79, via the opening 111, through the chamber89, between ball and valve seat, through the channel 91, the recess 80,the inner annular chamber 92 into the outer annular chamber 93. Innerand outer annular chambers are interconnected hydraulically. Pressurefluid flows from the outer annular chamber through the channel 94 to theunpressurized supply reservoir, see FIG. 1.

A control action takes place between ball and valve seat. Herein, theworking piston remains in a position shifted into the master cylinder.

As is known, working piston and brake pedal are interconnected by thebraking pressure booster and/or the pedal assembly. Hence follows thatneither the brake pedal is returned into its end position.

Pressure-relief of the working chamber 79 takes place as follows duringthe control mode:

The SO-valves and SG-valves of the pressure modulator are actuatedcorresponding to the control algorithm installed in the electroniccontrol unit. As a result, pressure fluid flows via the pressuremodulator back into the supply reservoir.

Pressure fluid flows via the line 94 into the supply reservoir throughthe regulating central valve disposed in the working piston of themaster cylinder.

A certain quantity of fluid discharges in the control mode through thethrottle bore 112 in the locking piston 86.

When the control mode is terminated, the pressure chamber 79 willexhaust as follows:

Pressure fluid discharges through the throttle bore 112. Besides,pressure fluid flows through the channel 94 into the supply reservoir.

A solenoid is illustrated in FIG. 4 which urges the piston 95 againstthe sleeve 70, the said piston serving as a fixing mechanism and beingprovided with the seal 114. This solenoid can be controlled by theelectronic control unit of the braking pressure regulating device. Thesolenoid is secured with its housing 101 to the master cylinder housing102.

When the coil 96 is excited due to a signal of the control unit, the endsurfaces of the armature 98 and of the pole core 99 oppositely disposedin the air gap 97 will be polarized. The resultant attractive forcemoves the armature in the direction of the arrow 100. Transmitted ontothe piston 95 is the contact force for fixing of the sleeve. Theresetting of the fixing mechanism, that means of the piston 95 of FIG.4, is effected by a current-off-signal of the electronic control unit.This eliminates the excitation of the magnet coil, and the spring 115resets the piston 95.

FIG. 5 shows a master cylinder housing attachment 103 which disposes ofa cylinder. This cylinder houses a vacuum chamber 104 as well as achamber with atmospheric pressure 105. Both chambers are isolated by aconverter piston 106. When vacuum is generated in the chamber 104 by thevacuum line 107, the piston 105 furnished with seal 116 and throttlebore 18 moves in the direction of the arrow 108. The sleeve will befixed, as is shown in respect with FIG. 3.

110 represents a pneumatic valve which governs the vacuum in chamber104. This pneumatic valve, in turn, is operated by the electroniccontrol unit of the braking pressure regulating device. Resetting of thepiston 105 takes place by ventilation via the line 7 at port 17.

Likewise in the embodiment according to FIG. 5, a throttle bore 18 canbe made use of analogously to the embodiment according to FIG. 3.

Several embodiments of the instant invention have been describedhereinabove. This invention is not limited to these embodiments. It isalso possible to choose other designs and arrangements for the sleevewith cross member serving as blocking unit. Further embodiments of thefixing mechanism for the sleeve are permitted within the scope of thisinvention, too. Thus, a variation of the embodiments according to FIGS.3, 4, 5 can be chosen, wherein further depression of the brake pedaland/or further release is possible. A reduction in overall length isachieved in that the fixing mechanism grips behind the sleeve. Theblocking unit may likewise be composed of several elements instead ofconsisting of one element, as it is displayed.

What is claimed is:
 1. A braking pressure regulating anti-lock controland traction slip control device for hydraulic brake systems ofautomotive vehicles, comprising in combination: a master cylinder withat least one working piston, and at least one working chamber, a supplyreservoir for pressure fluid, a pressure modulator for the variation ofthe hydraulic pressure in the wheel cylinders of the wheel brakes duringthe braking pressure control mode, said pressure modulator includinginlet and outlet valves for the wheel cylinders, an electronic controlunit for the control of the valves of the modulator, at least onemotor-driven pump for generating a hydraulic pressure, the workingchamber of the master cylinder being applied by pump pressure in thebraking pressure control mode and the working piston of the mastercylinder being movable in the direction of its initial position causedby the pump pressure, a regulating valve being provided in at least oneworking piston which, in the braking pressure control mode, regulatesthe pressure fluid flow in the hydraulic fluid cycle composed of the atleast one pump, the at least one working chamber of the master cylinderand the supply reservoir, including means for displacing the switchingpositions of the regulating valve incorporated in the working pistoninto the master cylinder in the braking pressure control mode.
 2. Abraking pressure regulating device as claimed in claim 1, wherein theregulating valve is composed of a valve seat, a valve closure member, atappet acting upon the valve member and opening the regulating valve,and a stop for the tappet, wherein in the braking pressure control mode,the stop for the tappet is arranged to move by predefined distances awayfrom its initial position into the master cylinder so that in thebraking pressure control mode the pressure fluid flow control in thehydraulic fluid cycle takes place at positions of the working pistonwhich are displaced into the master cylinder.
 3. A braking pressureregulating device as claimed in claim 2, wherein hydraulic actuatingmeans comprising a hydraulic piston-cylinder assembly applicable by thepump pressure is provided which positions the stop for the tappet in thedirection into the master cylinder at a predetermined distance in frontof its initial position.
 4. A braking pressure regulating device asclaimed in claim 2, wherein the stop for the tappet comprises a stopdevice which includes a movable direct stop member (56) and a movableindirect stop member (61).
 5. A braking pressure regulating device asclaimed in claim 4, wherein the movable stop member (61) is arranged tobe positioned by the pump pressure and by the force of a spring element(64).
 6. A braking pressure regulating device as claimed in claim 4,wherein a separate pressure chamber (59) is provided in the mastercylinder which is confined by the movable stop member (61) and is of avariable volume.
 7. A braking pressure regulating device as claimed inclaim 4 wherein the movable stop member (61) is provided as a pistonwhich is arranged displaceable by the pump pressure in opposition to theforce of a spring (64).
 8. A braking pressure regulating device asclaimed in claim 1 which comprises a vacuum brake power booster, whereina separate pressure chamber (59) is provided in the master cylinder (16)which is defined by the master cylinder housing, a displaceable piston(61) and the force-transmitting element (62) of the brake power booster(9).
 9. A braking pressure regulating device as claimed in claim 1,wherein a mechanical blocking unit is provided which is fixed in atleast one positions by a fixing mechanism and comprises a sleeve (70)accommodated in the master cylinder and having a stop element for thetappet of the regulating valve (72), said stop element comprises acomponent part (71) which is placed crossly to the axis of the mastercylinder (79) and is arranged as a pin, and which is located within saidsleeve (70).
 10. A braking pressure regulating device as claimed inclaim 1, wherein a fixing mechanism (86) is arranged in the mastercylinder housing displaceable radially in opposition to the sleeve (70),which fixes the sleeve (70) in at least one position by operativejamming engagement.
 11. A braking pressure regulating device as claimedin claim 1 wherein a fixing mechanism (86) is arranged in the mastercylinder housing displaceable radially in opposition to a sleeve (70),which fixes the sleeve (70) in at least one one position by positiveengagement by catching sleeve (70) thereby to fix the position of saidsleeve (70).
 12. A braking pressure regulating device as claimed inclaim 9, wherein the fixing mechanism is arranged as a piston (86) whichis guided in the master cylinder wall and is slidable by a hydraulicpiston-cylinder assembly (85, 84), with the piston-cylinder assemblybeing acted upon by the pressure fluid of the pump in the brakingpressure control mode.
 13. A braking pressure regulating device asclaimed in claim 9 wherein the fixing mechanism is designed as a piston(95) which is guided in the master cylinder wall (102) and isdisplaceable arranged by an electromagnetic lifting mechanism includinga magnet (96, 100, 101), with said lifting mechanism being controlled bythe electronic control unit of the braking pressure regulating device.14. A braking pressure regulating device as claimed in claim 9, whereinthe fixing mechanism is arranged as a piston (109) which is guided inthe master cylinder wall (102) and which is displaceable by the force ofa pneumatic converter (104, 106) which converts the difference betweenthe atmospheric pressure and the pressure below atmospheric pressure inone of the suction pipe of the internal combustion engine of theautomotive vehicle or a vacuum pump into a translatory force andtransmits it onto the piston (109), said pneumatic converter beingcontrolled by the electronic control unit of the braking pressureregulating device.